Effect of rf power on the properties of rf magnetron sputtered ZnO:Al thin films

Aluminum doped zinc oxide ZnO:Al thin films were prepared using rf magnetron sputtering. The preparation was performed at room temperature and low pressure with varying rf power between P = 50 W and P = 500 W. Structural, electrical and optical film properties were studied depending on rf power. Special attention was paid to correlations among film structure, sheet resistance and optical transmission. Films with largest crystallite size exhibited highest optical transmission, but not lowest electrical resistivity. An explanation for this finding was sought in terms of the amount of Al atoms incorporated in the films and the places they occupy, parameters which are in turn related to rf power. -- Highlights: ► Al-doped ZnO thin films were prepared by rf sputtering depending on rf power. ► Films with largest crystallite size exhibited highest optical transmission. ► These films did not exhibit lowest electrical resistivity! ► Resistivity was more correlated with interplanar spacing than with crystallite size. ► The incorporation of Al atoms and the places they occupy may explain this behavior.